Constructing a flawless concrete slab doesn't require knowing all the secrets of the universe, but it helps if you have some basic understanding. Here are several common questions.

1. What are some best practices when it comes to concrete slab construction?
Invariably there are many answers to this question. Here are several tips you or your crew members might not be aware of including how common mistakes can be avoided with proper base preparation, mix design, placement, finishing, and curing.

2. What makes post-tensioned concrete slabs so strong? If you work with post-tensioned concrete slabs, it can be useful to understand the basic physics behind the material. As one expert, Jim Rogers, explains here, post-tensioned concrete slabs maximize the strengths of both concrete and the steel applying push (compressive) forces to the concrete and pull (tensile) forces to the steel.

3. What reinforcement system should I use for a slab? There are many opinions as to the benefits, or lack thereof, of reinforcement for slabs on ground, but understand the limitations. There are several reinforcement systems, and each has unique pros and cons.

4. How should I time a garage floor job? Timing is everything. This schedule should help ensure that your job stays on track.

  • Place concrete within 90 minutes after it leaves the ready-mix plant.
  • Screed immediately after spreading and consolidating concrete.
  • Bull-float or darby as soon as possible after screeding and before bleedwater appears.
  • Allow all bleedwater to rise to the surface and evaporate; concrete should be hardened enough so that footprints are 1/4 inch deep or less.
  • Edge the concrete and cut tooled joints, if desired (not necessary if saw-cutting joints).
  • Float the concrete to embed aggregate, remove imperfections, and consolidate surface.
  • Trowel to produce a hard, flat surface.
  • Saw joints with early-entry saw in one to four hours.
  • Saw joints with traditional wet-cut saw after four to 12 hours (as soon as concrete can be sawed without aggregate loosening).

5. Explain the relationship between concrete strength and slab thickness. There is a definite correlation between the two and engineering specifications require some specific mathematical calculations. Consider this example.